jfd
Newbie level 1
DALI (Digital Addressable Lighting Interface) is used primarily to control architectural lighting, more background at this Wikipedia page including a link to draft standard.
Since DALI is not defined as SELV "and therefore can be run next to the mains carrying cables or a part of a multi-core cable that includes mains power", in practice, this means that opto-isolation is required between the DALI bus and the µC. Atmel, Cypress, NXP and ST all have pretty similar circuit diagrams in their app notes. (There is a non-isolated implementation in a Freescale/Motorola appnote, which doesn't address isolation, but does provide DALI bus power.)
So my question is simple really, should I put overvoltage protection in my interface to protect from a wiring fault that could lead to mains voltages down a DALI signal cable? Since the DALI Bus is going to act like a long antenna in the roof, doesn't it make sense to incorporate lightning protection too?
I'm thinking of using a GDT between the lines, followed by resettable fuses on each line for primary protection and subsequently opposing TVS diodes between the signal lines for secondary protection. This is for a one off installation, not in a particularly lightning prone area, but I don't want it to be unreliable.
Is there anyone with experience in surge protection out there, who would care to comment on the likely effectiveness and utility of this arrangement? Also, the Atmel reference design for a DALI ballast doesn't address surge protection. If that's typical of commercial designs, surely that would have field reliability implications.
Thanks, j.
Since DALI is not defined as SELV "and therefore can be run next to the mains carrying cables or a part of a multi-core cable that includes mains power", in practice, this means that opto-isolation is required between the DALI bus and the µC. Atmel, Cypress, NXP and ST all have pretty similar circuit diagrams in their app notes. (There is a non-isolated implementation in a Freescale/Motorola appnote, which doesn't address isolation, but does provide DALI bus power.)
So my question is simple really, should I put overvoltage protection in my interface to protect from a wiring fault that could lead to mains voltages down a DALI signal cable? Since the DALI Bus is going to act like a long antenna in the roof, doesn't it make sense to incorporate lightning protection too?
I'm thinking of using a GDT between the lines, followed by resettable fuses on each line for primary protection and subsequently opposing TVS diodes between the signal lines for secondary protection. This is for a one off installation, not in a particularly lightning prone area, but I don't want it to be unreliable.
Is there anyone with experience in surge protection out there, who would care to comment on the likely effectiveness and utility of this arrangement? Also, the Atmel reference design for a DALI ballast doesn't address surge protection. If that's typical of commercial designs, surely that would have field reliability implications.
Thanks, j.
